Wait time is now fully server-controlled via default_wait_seconds setting.
Agents can no longer request a different wait duration - only the user
controls this via the web UI.
- Remove wait_seconds param from get_user_request signature
- Simplify actual_wait to min(cfg.default_wait_seconds, MAX_WAIT)
- Update Settings panel label from 'Min Wait' to 'Wait (sec)'
- Update hint text to explain server-only control
- Update README: input schema, behavior rules, settings description, changelog
